If you're using a mobile try Aviary.
It's a popular photo editor with a good set of features and reliability. The quick and easy way is the one-touch enhance mode but it also comes with a variety of manual adjustments to let you do things like adjust the color, brightness, temperature, contrast, saturation etc. It also comes with stickers, filters, and tools such as red eye fixing, blemish remover, and teeth whitener.
If you are using a computer, nothing can beat Photoshop. Tutorials of how to fix photos are widely available on the internet. Or you can check on this site https://en.tuto.com/